#pragma once
#include<assert.h>
#include<string.h>
namespace zjw
{
	class string
	{public:
		typedef char* iterator;
		typedef const char* const_iterator;
		iterator begin()
		{
			return _str;
		
		}
		iterator end()
		{
			return _str + _size;
		
		}
		const_iterator begin() const
		{
			return _str;

		}
		const_iterator end()  const
		{
			return _str + _size;

		}
		string(const char* str = "")
			:_size(strlen(str))
		{
			_capacity = _size;
			_str = new char[_capacity + 1];
			strcpy(_str, str);

		
		
		
		
		
		}
		~string()
		{
			delete[]_str;
			_str = nullptr;
			_size = _capacity = 0;

		}
		size_t size()
		{
			return _size;
		
		}
		size_t capacity()
		{
			return _capacity;
		
		}
		char& operator[](size_t pos)
		{
			assert(pos < _size);
			return _str[pos];
		
		
		}
		const char& operator[](size_t pos) const
		{
			assert(pos < _size);
			return _str[pos];


		}
		const char* c_str()
		{
			return _str;
		}
		void reserve(size_t n)
		{
			if (n >_capacity)
			{
				char* tmp = new char[n + 1];
				strcpy(tmp, _str);
				delete[] _str;
				_str = tmp;
				_capacity = n;


			}
		
		
		
		
		
		
		}
		void push_back(char ch)
		{
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 : 2 * _capacity);




			}
			_str[_size] = ch;
			++_size;
			_str[_size] = '\0';
		}
		void append(const char* str)
		{
			size_t len = strlen(str);
			if (_size + len > _capacity)
			{
				reserve(_size + len);

			}
			strcpy(_str + _size, str);
			_size += len;
		}
		string& operator+=(char ch)
		{
			append(_str);
			return *this;
		
		
		
		}
	/*	string& operator+=(const char* str)
		{
			append(str);
			return *this;
		
		
		}*/
		void insert(size_t pos, char ch)
		{
			assert(pos <= _size);
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 : 2 * _capacity);

			}
		/*	size_t end = _size;
			while (end >= pos)
			{
				_str[end + 1] = _str[end];
				end--;
			}*/
			size_t end = _size + 1;
			while (end > pos)
			{
				_str[end] = _str[end - 1];
				--end;




			}
			_str[pos] = ch;
			++_size;


		
		
		
		
		}
		void erase(size_t pos, size_t len=npos)
		{
			assert(pos < _size);
			if (len == npos || len >= _size - pos)
			{
				_str[pos] = '\0';
				_size = pos;



			}
			else
			{
				strcpy(_str + pos, _str + pos + len);
				_size -= len;





			}
		
		
		
		
		}


		


      


	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	public:
		static const int npos;










	};

	const int string::npos = -1;










}
